The improvement of fuel efficiency or engine brake performance of an internal combustion engine is a primary concern of engine manufacturers, end users, and regulatory agencies. Many attempts have been aimed at improving the fuel efficiency of internal combustion engines. However, in many instances, such improvements to the fuel efficiency of an engine often come at the expense of one or more other performance characteristics of the engine. In other words, measures to improve the fuel efficiency of an internal combustion engine may place various operational and performance limitations on the engines.
Generally, the amount of fuel consumed by an engine, which is directly related to the fuel efficiency of the engine, is determined based on one or more predetermined control surfaces. Each control surface includes precalibrated values for the fuel injection and air handling systems for various engine speed and engine load combinations within the operating range of the engine. The operating range of the engine is also predetermined and is typically referred to as a torque-speed curve. The torque-speed curve constrains operation of the engine to a range of engine speed and engine load combinations. For example, the torque-speed curve may limit the maximum engine speed or load to improve fuel efficiency, among other reasons. Notwithstanding the potential improvements to the fuel efficiency of the engine by instituting speed and load limitations on the engine, other performance characteristics and/or operations may suffer or be correspondingly limited.